Mercury wetted switch

ABSTRACT

A switch assembly comprising a housing including a baseplate on which are mounted a magnetic core having a pair of flanges and a winding wound around it, and two switch capsules positioned on either sides of the magnetic core with each capsule being insulated from each flange of the magnetic core by insulating means. Magnets are also positioned to provide either a monostable or a bistable mode of operation as desired. With this constructions, the magnetic and electric paths in the assembly are physically separate from one another, thereby allowing the magnetic and electric materials to be chosen independently from each other.

FIELD OF THE INVENTION

The present invention relates to a mercury wetted switch assembly whichis capable of operation in any position.

BACKGROUND OF THE INVENTION

A typical mercury wetted switch comprises a sealed glass capsule inwhich there is mounted a movable armature having a pair of pole ends foralternately contacting a respective electric contact when the armatureis pivoting and the surface of the armature is wetted with a film ofmercury. An energizing coil is provided to generate magnetic field inthe magnetic conducting parts in order to generate a magnetic forcewhich tends to operate the switch. The mode of operation, eithermonostable or bistable, is creating by externally positioning one or twopermanent magnets to the capsule.

The reeds used in the capsule for making the switching contacts are tobe made of a material that must be carefully chosen in order to meetthree requirements:

1) it must be optimally magnetic conducting,

2) it must be optimally electric conducting,

3) it must have an expansion coefficient that is compatible with that ofglass.

In practice, the choice of the material for the reeds is a compromisebetween the said three requirements and can never optimally meet all andeach of them.

SUMMARY OF THE INVENTION

The object of this invention is to provide a mercury wetted switchconstruction in which the magnetic and electric paths are as much aspossible separate from each other thereby allowing the magnetic andelectric materials to be optimally chosen independently from oneanother.

It is another object of this invention to provide a mercury wettedswitch construction in which the magnetic and electric paths are as muchas possible separate from each other thereby making it possible toachieve better magnetic and electrical characteristics.

These objects are attained in accordance with the invention with amercury wetted switch assembly as defined in the claims.

In particular, there is provided a switch assembly comprising a housingincluding a baseplate. On the baseplate are mounted a magnetic corehaving a pair of flanges and a winding wound around it, and two switchcapsules positioned on either sides of the magnetic core with eachcapsule being insulated from each flange of the magnetic core byinsulating means. Magnets are also positioned to provide either amonostable or a bistable mode of operation as desired. With thisconstruction, the magnetic and electric paths in the assembly arephysically separated from one another, thereby allowing the magnetic andelectric materials to be chosen independently from each other.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of an exemplary embodiment of the switch assemblyin accordance with the invention.

FIG. 2 is a cross-sectional view along line II--II in FIG. 1.

FIG. 3 is a side view of tile switch assembly of FIG. 1.

FIG. 4 is a bottom view of one of the capsules shown in FIG. 1.

FIG. 5 is a cross-sectional view along line V--V in FIG. 4.

FIG. 6 is a partially stripped view of a capsule shown in FIG. 1.

DESCRIPTION OF AN EXEMPLARY EMBODIMENT

Referring to FIGS. 1 and 2 it is shown that the switch assemblyaccording to the invention essentially comprises a magnetic unit 10 andtwo switch capsules 20 which are mounted on either sides of the magneticunit 10. The whole assembly is housed in an envelope or housing 16 withterminals 15 projecting therefrom.

The magnetic unit 10 includes a I-shaped magnetic core 11 having awinding 17 directly wound around it and end flanges 12 made of the samemagnetic material. Each switch capsule 20 is insulated from the flanges12 of the magnetic core by means of insulating tapes 13 (FIG. 2) wherebythe magnetic and electric paths are physically separated from eachother. This construction allows the magnetic and electric conductingmaterials to be optimally chosen independently from one another.

Each switch capsule 20 is arranged as shown in FIGS. 4, 5 and 6. Thecapsule comprises a ceramic plate 21 having a recess 22 formed thereinfor accommodation of a cantilever beam 23 in such a manner that it iscapable of pivoting movement with a minimum clearance between the beamand the ceramic plate. The beam 23 has a pair of pole ends foralternately contacting a respective electric contact when the beam ispivoting. A spring 28 is positioned on the cantilever beam 23 in orderto centering the beam 23 within the ceramic housing and also to apply ahigh acceptable return force when a contact is caused to break. Thesurface of the cantilever beam 23 is wetted with a film of mercury. Thisconstruction is effective to prevent an excess of mercury to be splashedonto the ceramic surfaces thereabout whereby greater switchingreliability is secured.

The ceramic plate 21 is surrounded with metal foils: an upper metal foil25 on the top surface and three spaced apart contacting foils 26 on theopposite surface. The inner side of the two outer contacting foils 26are provided with at least three mercury-wetted elongated contact spots27. Simultaneous contacts can be arranged thereby making it possible toswitch very high load currents.

The cantilever beam 23 has a lengthwise extending capillary groove 24formed therein for allowing mercury to be distributed to the switchingareas. The terminals 15 are directly connected to the capsules 20whereby these terminals are physically independent from the windingconstruction.

A magnet 14 is externally positioned to each capsule 20 thereby toprovide a normal magnetic make position of the switch. Providing twomagnets on the capsules makes it possible to secure a bistable mode ofoperation which requires a magnetic balance in the system.

I claim:
 1. A mercury-wetted switch assembly, comprising:a housing; abaseplate inside the housing; a winding construction including amagnetic core mounted on the baseplate and having a pair of end flanges,and a winding wound directly around said core; a pair of mercury-wettedswitch capsules mounted on the baseplate with one capsule beingpositioned on either side of the magnetic core, each capsule beinginsulated from each of the flanges of the magnetic core by insulatingmeans; at least one of said capsules having at least one magnetexternally positioned to the capsule; and each of said capsules havingterminals connected directly to the capsule and projecting from thehousing, whereby said terminals are physically independent from thewinding construction.
 2. A switch assembly as claimed in claim 1,wherein each of the switch capsules includes a ceramic plate having arecess formed therein for accommodation of a cantilever beam mountedsuch that said beam is capable of pivoting movement, said beam having apair of pole ends for alternately contacting a respective electriccontact when the beam is pivoting, a surface of said beam being wettedwith a film of mercury.
 3. A switch assembly as claimed in claim 2,wherein the pole ends of the cantilever beam are provided withmercury-wetted contact spots.
 4. A switch assembly as claimed in claim2, wherein the cantilever beam is provided with a lengthwise groove forallowing distribution of mercury to the switching areas.
 5. A switchassembly as claimed in claim 4, wherein the pole ends of the cantileverbeam are provided with mercury-wetted contact spots.